1. Industrial Field of the Invention
The present invention relates to a check valve of a fuel tank, which is provided on an end portion of a fuel supply pipe for introducing fuel to the fuel tank, which end portion is located inside of the tank.
2. Description of the Prior Art
In order to prevent liquid fuel from flowing back to a fuel supply port due to an increase in the tank internal pressure at the time of fuel supply or the like, a check valve is provided in a fuel supply passage, and this check valve has a mechanism to be open when fuel flows normally during fuel supply and to be closed when fuel flows back.
Conventionally, for example, there have been a check valve comprising two semicircular valve plates, as disclosed in U.S. Pat. Nos. 4,774,981 and 4,977,926, a check valve which is opened and closed like an alligator's mouth, as disclosed in U.S. Pat. No. 5,044,396, and a check valve comprising a circular valve plate similar to the present invention, as disclosed in U.S. Pat. No. 4,989,635. As obviously understood from these examples, a valve plate is generally attached to joints by means of a pin. In this method, however, the pin must be designed not to come off after the assembly. Therefore, the pin must be press-fitted into the joints, or the pin must be processed afterwards, for example, by crushing the tip of the pin. Moreover, a check valve is attached to a fuel supply pipe by welding or press-fitting the valve into the pipe or fixing the valve by fasteners, which is a difficult operation to be performed in a sealed tank.
Especially, a check valve of the type which is attached to an end portion of a fuel pipe which is projected into a tank, as in this invention, is different from a check valve of the type which is provided inside of the fuel passage in that fuel collides against the valve plate forcefully, splashes in all directions and falls into the tank. If a large amount of fuel splashes, a large amount of fuel vapor will be generated in the tank, so that prevention devices must be provided not to destroy the natural environment by diffusion of fuel gas. Consequently, fuel splash must be suppressed to prevent generation of fuel vapor as much as possible.